Nielsen has for years sought ways to measure the interplay of social media activity and TV viewing. Its new “multi-year” deal with Twitter is a tacit acknowledgement that Nielsen can't close the media measurement loop on its own.

There's a similar observation to made about this morning’s announcement that Nielsen is buying long-time audience measurement rival, Arbitron, known for its radio ratings. The $1.26 billion purchase helps Nielsen solidify its dominance across all media, traditional and new. Read the release.

With Arbitron's assets, Nielsen intends to further expand its “Watch” segment’s audience measurement across screens and forms of listening. “These integrated, innovative capabilities will enable broader measurement of consumer media behavior in more markets around the world," said Steve Hasker, Nielsen President of Global Media Products and Advertiser Solutions, in a statement. "We will also bring local clients greater visibility to empower more precise advertising placement and campaign effectiveness.”

While Nielsen’s tie-in with Twitter is less dramatic than the acquisition of Arbitron, it could ultimately be just as important, given the microblog’s centrality as a point of discussion among web users.

The two companies will develop a “Nielsen Twitter TV Rating” for the U.S. market for next year’s fall primetime season. The goal is to sell advertisers on a syndicated metric around the reach of the TV conversation on Twitter that is intended to be recognized as “the standard” for social TV.

With this arrangement in place well before the spring upfront negotiations, Nielsen hopes to be able to present a hard number that tells brands what shows are trending with whom. That may still have only a little influence on what marketers and media buyers agree to spend on TV, but it could have significant impact on where cross-platform ad dollars go. When it comes to social media ad spending, Facebook is where most of the action is. But Twitter’s more aggressive push into marketing and promotions is starting to make it more attractive to advertisers.

The Nielsen Twitter TV Rating is being discussed as a complement to Nielsen’s existing TV ratings. Nielsen is positioning these adjunct ratings to TV networks and advertisers as an example of real-time metrics that are necessary to understand TV audience on a deeper level, namely through their social activity. The actual system is being built on top of NM Incite’s SocialGuide audience engagement analytics platform. NM Incite is another important deal Nielsen signed earlier this year as a joint venture between it and McKinsey & Co.

Among other things, the partnership could help advertisers figure out how mobile can be a better value to brand advertisers.

"While many of the details of Nielsen's Social TV Ratings are yet to reveal themselves, we are excited to see further development in this space," said Brian Monahan, Managing Partner, Intelligence Practice, Magna Global. "We've been using social data at the TV show level for the last few years to inform TV planning and buying. While we do not use social chatter as a raw ranker for show selection, we do combine it with other signals for more effective TV investments. Before we apply our proprietary algorithms, we have an operational challenge of simply associating social activity data to the granular show level. At the very least, we hope a Nielsen Social TV rating makes it easier for our systems to ingest a full data set."

The increasing focus on mobile by both Twitter and Facebook, as well as mainstream media outlets, is what’s driving growth in the overall U.S. mobile advertising market, which eMarketer estimates will reach $4.1 billion this year. By 2016, the U.S. mobile advertising market is expected to near $21 billion, according to eMarketer.

In general, marketing is becoming more and more real-time oriented. In that sense, the thought of spending many millions on TV ads and then waiting a month to get a report of how it performed is not that helpful. Although there’s no question that Twitter is firmly mainstream, most of the regular daily tweets are driven by a small subset of devoted users – in other words, these avid Twitter users may not necessarily correspond directly to the actual shape of TV viewing audiences.

That’s not to say it can’t help with younger, increasingly hard-to-reach demos. For example, that tracking TV ads in real-time to better understand the value of launching an ad at a precise moment in time has obvious value. Questions such as “How much weight are they putting behind this creative versus that creative?” can be understood almost immediately through this kind of system.

And while a network can’t optimize TV at the same time it can optimize the display ads, real-time information can help media companies and brands plan their sales strategies with a lot more clarity.

Overall, the question of how best to attach paid media to earned media is something that is still going to be a big challenge. Marketers are at wit’s end trying to figure out ways to create and monitor conversations around their brands. Whether Nielsen can satisfy those demands has yet to be determined, but the depth of its resources is unmatched.

"Nielsen's development of social TV ratings is natural and a precursor of the same for Video,” former Kantar head Bill Lederer, currently chairman and CEO of MediaCrossing, told AdExchanger. “We at MediaCrossing suspect this effort will benefit media sellers and the social ecosystem more than media buyers as the former seeks to differentiate their offers and compensate for increasingly fragmented audiences and higher CPMs on the basis of viewer engagement and sentiment than might be justified otherwise."